Semiconductor and other similar industries, often use optical metrology equipment to provide non-contact evaluation of substrates during processing. With optical metrology, a sample under test is illuminated with light. After interacting with the sample, the resulting light is detected and analyzed to determine a desired characteristic of the sample.
Some optical metrology systems use multiple wavelengths of light, either simultaneously or sequentially, e.g., in multiple narrow bandwidths. Light sources that produce multiple wavelengths of light in optical metrology systems sometimes use a combination of multiple light sources, each producing a different range of wavelengths. If one or more of these multiple light sources malfunction, e.g., either fail to produce light or produce light with an incorrect wavelength, the resulting measurements generated by the optical metrology device may be adversely affected.